Circuits having ECL-technology devices are characterized by features such as high operating speed, medium to high integration degree and medium to high power dissipation/power losses. However, circuits having FET-technology devices with merely medium operating speeds are known for having a very high integration degree and very low power losses. These last features have made it desireable to increase the speeds of integrated circuits having FET-technology devices to a level which so far has been only possible using bipolar technology devices.
For broadband signal switching equipment with a switching point matrix having matrix input lines respectively constituted by two signal conductors, these matrix input lines on the one hand are connected respectively to two differential (complementary) outputs of a digital input signal circuit, and on the other hand, are connectable, via switching points, to matrix output lines also constituted by two signal conductors. These matrix output lines having two signal conductors are connected to the two signal inputs of an output amplifier circuit constituted by a differential amplifier. A switching point matrix having FET-technology devices is disclosed in European reference EP-A-0 264 046 (corresponding to U.S. Pat. No. 4,897,645) wherein switching element couples are provided in the switching points and have, respectively, two switch transistors which receive on their control electrode a throughput signal or a blocking signal. The switch transistors of these switching element couples are connected with one main electrode respectively to one or the other signal conductor of the appertaining matrix output line which in turn is provided with an output differential amplifier with a trigger characteristic, whereby the switching element couples have two auxiliary transistors, respectively, which form a series connection with one switch transistor, these auxiliary transistors have their to the control electrodes connected to one or the other signal conductor of the appertaining matrix input line. One of their main electrodes is connected to one terminal (ground) of the operating voltage source, the other terminal being connected to each signal conductor of the respective matrix output line, respectively, via one precharge transistor. Precharge transistors and sampling transistors are charged oppositely to one another on their control electrodes with a selection clock for switching matrix arrays thereby dividing a bit-throughput-interval into a precharge phase and an actual throughput phase. As a result in each precharge phase for a blocked sampling transistor both signal conductors of the matrix output line are charged, at least approximately, to the potential at the other terminal of the operating voltage source, via the respective precharge transistor.
In addition to the advantages which are associated with a switching point matrix having FET-technology devices, this known broadband signal switching equipment has the further advantage that on one hand, for a blocked switching point, no interfering signals reach the matrix output via the switching point even without additional attenuation measures and that, on the other hand, for a conducting switching point and when the actual throughput occurs, recharging of the matrix output line always results in a recharging direction from the operating potential corresponding to the signal condition. This occurs even with a small recharging/charge reversal (corresponding to surpassing a threshold at this operating potential value and corresponding to the trigger point of the differential amplifier). Thus just as quickly a clean transition of the throughconnected digital signal occurs at the output of the switching equipment from one into the other signal condition.
In the case of such a broadband signal switching equipment a further increase in the operating speed can be provided in that the two precharge transistors, at their main electrodes facing the respective matrix output line, are connected with each other via a cross transistor, whose control electrode is connected to the control electrodes of the precharge transistors (disclosed in German reference DE-P 3819491.0) (corresponding to U.S. Pat. No. 4,949,086). In connection with the advantage of an acceleration of the precharging of the matrix output lines, there is also the further advantage of a very early potential balancing of the matrix output lines so that there is also correspondingly early starting conditions for good amplification via a following differential amplifier.
A further increase of the operating speed of the broadband signal switching equipment is achieved if in addition to a sampling transistor provided individually for the matrix input line, a precharge transistor, provided individually for the matrix input line, is used or, as an alternative, a precharge transistor, provided individually for the matrix output line, is used in addition to a sampling transistor provided individually for the matrix output line (disclosed in German reference DE-P 3819491.0).
The advantages of such known broadband signal switching equipment, which have matrix input lines respectively constituted by two signal conductors, that can be achieved regarding the power dissipation requirement and operating speed are associated with a corresponding space requirement for such matrix input lines, which respectively have two signal conductors. The present invention, however, provides a means for significantly reducing this space requirement.